random: rate limit unseeded randomness warnings

On systems without sufficient boot randomness, no point spamming dmesg.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

1 files changed, 34 insertions, 5 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 721dca8db9cf..cd888d4ee605 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -261,6 +261,7 @@
 #include <linux/ptrace.h>
 #include <linux/workqueue.h>
 #include <linux/irq.h>
+#include <linux/ratelimit.h>
 #include <linux/syscalls.h>
 #include <linux/completion.h>
 #include <linux/uuid.h>
@@ -438,6 +439,16 @@ static void _crng_backtrack_protect(struct crng_state *crng,
 static void process_random_ready_list(void);
 static void _get_random_bytes(void *buf, int nbytes);
 
+static struct ratelimit_state unseeded_warning =
+        RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
+static struct ratelimit_state urandom_warning =
+        RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
+
+static int ratelimit_disable __read_mostly;
+
+module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
+MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
+
 /**********************************************************************
  *
  * OS independent entropy store.   Here are the functions which handle
@@ -932,6 +943,18 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
                 process_random_ready_list();
                 wake_up_interruptible(&crng_init_wait);
                 pr_notice("random: crng init done\n");
+                if (unseeded_warning.missed) {
+                        pr_notice("random: %d get_random_xx warning(s) missed "
+                                  "due to ratelimiting\n",
+                                  unseeded_warning.missed);
+                        unseeded_warning.missed = 0;
+                }
+                if (urandom_warning.missed) {
+                        pr_notice("random: %d urandom warning(s) missed "
+                                  "due to ratelimiting\n",
+                                  urandom_warning.missed);
+                        urandom_warning.missed = 0;
+                }
         }
 }
 
@@ -1572,8 +1595,9 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller,
 #ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
         print_once = true;
 #endif
-        pr_notice("random: %s called from %pS with crng_init=%d\n",
-                  func_name, caller, crng_init);
+        if (__ratelimit(&unseeded_warning))
+                pr_notice("random: %s called from %pS with crng_init=%d\n",
+                          func_name, caller, crng_init);
 }
 
 /*
@@ -1767,6 +1791,10 @@ static int rand_initialize(void)
         init_std_data(&blocking_pool);
         crng_initialize(&primary_crng);
         crng_global_init_time = jiffies;
+        if (ratelimit_disable) {
+                urandom_warning.interval = 0;
+                unseeded_warning.interval = 0;
+        }
         return 0;
 }
 early_initcall(rand_initialize);
@@ -1834,9 +1862,10 @@ urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 
         if (!crng_ready() && maxwarn > 0) {
                 maxwarn--;
-                printk(KERN_NOTICE "random: %s: uninitialized urandom read "
-                       "(%zd bytes read)\n",
-                       current->comm, nbytes);
+                if (__ratelimit(&urandom_warning))
+                        printk(KERN_NOTICE "random: %s: uninitialized "
+                               "urandom read (%zd bytes read)\n",
+                               current->comm, nbytes);
                 spin_lock_irqsave(&primary_crng.lock, flags);
                 crng_init_cnt = 0;
                 spin_unlock_irqrestore(&primary_crng.lock, flags);